Island find may save bat species

Endangered: It was predicted the South Island long-tailed bat would be extinct within 50 years.

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A large colony of endangered South Island long-tailed bats has been found on D'Urville Island in the Marlborough Sounds - dramatically raising hopes the species can be saved from extinction.

The colony is estimated to number in the hundreds.

It was discovered by a Forest and Bird team last month during the fifth and final year of bat surveys, initiated by Forest & Bird top of the south field officer Debs Martin, alongside bat scientist Dr Brian Lloyd.

Bat boxes with special microphones were placed on the island in December and removed last month and audio-files revealed the presence of a bat colony.

"This find is fantastic news," Ms Martin said.

"It means that D'Urville Island is even more important to New Zealand's natural heritage than we thought."

Only 10 colonies of long-tailed bats are known to remain in the South Island mainland, with total numbers less than 5000 - and declining.

"D'Urville Island is the fifth largest island in New Zealand. One third of it is public conservation land," Ms Martin said.

"It is free of possums and ship rats, which increases the long-tailed bat's chances of survival. Except for a small colony on Stewart Island, the D'Urville group is the only one known to be living on an offshore island.

"This find dramatically increases the chances of saving the species from extinction.

"It was predicted that the South Island long-tailed bat would become extinct within 50 years.

"But this find may well alter that."

Ms Martin said Forest & Bird's next step would be working with the Department of Conservation, Ngati Koata and local landowners to monitor the bats and ensure the island remained a safe haven for the animals.

"Protecting the quality of the island's remaining forests and not allowing any new predator species to establish themselves on the island is now vital."

The fact the island was free of predator possums and ship rats had likely contributed to it being a haven for bats.

Forest & Bird also hoped to get funding to monitor the D'Urville Island population, to determine whether it was stable or declining.

"There is so much we don't know about. If the population is declining we would have to look at what might be causing that decline."

The D'Urville colony was found thanks to the late Colin Iles, whose estate funded the final year of bat surveys.

Other long-tailed bat colonies had been found at Pelorus, Lake Matiri and Mokihinui, and in places in the Kahurangi National Park.

One species of native bat, the greater short-tailed bat, became extinct in 1965 from predation by ship rats.

Another species of short-tailed bat survives, but in low numbers. Forest & Bird surveys have failed to find any surviving populations of short-tailed bats at the top of the South Island, including in places where it was known to have lived.